Alternate polarity kickless cables are well known in the art and are widely used to connect, for example, welding guns to transformers. Such cables have a number of stranded conductors or individual cables which alternate in polarity. The above Talley patent discloses six alternate polarity conductor strands. A star separator isolates the adjacent cables which are connected to high current capacity end terminals or lugs which are semi-circular and which are mutually electrically insulated along a diameter. Since every other conductor strand has to be connected to opposite halves, the cable termination presents a complex connection which also happens to be the usual point of wear or failure limiting the service life of the cable. While the design of the cables is to minimize the kicking or twisting which occurs during each welding cycle, some, nonetheless occurs. Also, a major application of such welding cables is in robotic welders. In such applications, the welding head may move into many different positions, again requiring the cable to flex or twist. It is therefore important that the overall cable be sufficiently flexible to permit the required movements, yet it is also important that stress concentrations at the terminations be minimized to the extent possible.
The cable and termination shown in prior U.S. Pat. No. 4,199,653 to Talley presents an efficient termination in that it avoids twisting individual conductors or strands to obtain the alternate polarity. In Talley, of the six conductors, two sets of two conductors or strands are provided with each set of two including end fittings. There are also two individual conductors each mounted in a fitting, or six strands all together. The fittings and mounting surfaces on the two termination halves are arranged such that a single conductor fitting mounted on one half nests that single conductor slightly radially outwardly and between the two conductors of a two conductor fitting mounted on the opposite half. In this manner, the conductors do not have to twist or weave around each other and the cable is easier to construct as well as to repair. The strand terminal fittings are readily mounted on the appropriate platforms on the respective termination half lugs using fasteners.
While the cable of the Talley patent has many advantages, one drawback is the use of single fasteners, particularly on the strand termination fitting for the dual strand set. This fitting carries twice the current of a single strand fitting and it has been found that over the life of the cable, particularly in robotic applications, the single fastener in the dual strand fitting may tend to loosen. If it does, the single fastener then may become a pivot point for unwanted relative movement. Although the cable can quickly be repaired, the unscheduled down time, however short, in a production line using robotics machinery is something to be avoided or at least minimized. One way to minimize such down time is to increase the service life of the cable.
Accordingly it would be highly desirable to have a water cooled kickless cable of the type shown in the prior Talley patent but which would have a superior service life while at the same time provide improved efficiency.